Design and synthesis of thermally stable single atom catalysts for thermochemical CO_(2) reduction

The continuous and excessive emission of CO_(2)into the atmosphere presents a pressing challenge for global sustainable development.In response,researchers have been devoting significant efforts to develop methods for converting CO_(2)into valuable chemicals and fuels.These conversions have the potential to establish a closed artificial carbon cycle and provide an alternative resource to depleting fossil fuels.Among the various conversion routes,thermochemical CO_(2)reduction stands out as a promising candidate for industrialization.Within the realm of heterogeneous catalysis,single atom catalysts(SACs)have garnered significant attention.The utilization of SACs offers tremendous potential for enhancing catalytic performance.To achieve optimal activity and selectivity of SACs in CO_(2)thermochemical reduction reactions,a comprehensive understanding of key factors such as single atom metal-support interactions,chemical coordination,and accessibility of active sites is crucial.Despite extensive research in this field,the atomic-scale reaction mechanisms in different chemical environments remain largely unexplored.While SACs have been found successful applications in electrochemical and photochemical CO_(2)reduction reactions,their implementation in thermochemical CO_(2)reduction encounters challenges due to the sintering and/or agglomeration effects that occur at elevated temperatures.In this review,we present a unique approach that combines theoretical understanding with experimental strategies to guide researchers in the design of controlled and thermally stable SACs.By elucidating the underlying principles,we aim to enable the creation of SACs that exhibit stable and efficient catalytic activity for thermochemical CO_(2)reduction reactions.Subsequently,we provide a comprehensive overview of recent literature on noble metal-and transition metal-based SACs for thermochemical CO_(2)reduction.The current review is focused on certain CO_(2)-derived products involving one step reduction only for simplicity and for better understanding the SACs enhancement mechanism.We emphasize various synthesis methods employed and highlight the catalytic activity of these SACs.Finally,we delve into the perspectives and challenges associated with SACs in the context of thermochemical CO_(2)reduction reactions,providing valuable insights for future research endeavor.Through this review,we aim to contribute to the advancement of SACs in the field of thermochemical CO_(2)reduction,shedding light on their potential as effective catalysts and addressing the challenges that need to be overcome for their successful implementation as paradigm shift in catalysis.

Multifunctional characteristics of 3D printed polymer nanocomposites under monotonic and cyclic compression

This study presents the multifunctional characteristics of multi-walled carbon nanotube(MWCNT)/polypropylene random copolymer(PPR) composites enabled via fused filament fabrication(FFF) under monotonic and quasi-static cyclic compression. Utilizing in-house MWCNT-engineered PPR filament feedstocks, both bulk and cellular composites were realized. The morphological features of nanocomposites were examined via scanning electron microscopy, which reveals that MWCNTs are uniformly dispersed. The uniformly dispersed MWCNTs forms an electrically conductive network within the PPR matrix, and the resulting nanocomposite shows good electrical conductivity(~10^(-1)S/cm), improved mechanical performance(modulus increases by 125% and compressive strength increases by 25% for 8 wt% MWCNT loading) and pronounced piezoresistive response(gauge factor of 27.9-8.5 for bulk samples)under compression. The influence of strain rate on the piezoresistive response of bulk samples(4 wt% of MWCNT) under compression was also measured. Under repeated cyclic compression(2% constant strain amplitude), the nanocomposite exhibited stable piezoresistive performance up to 100 cycles. The piezoresistive response under repeated cyclic loading with increasing strain amplitude of was also assessed.The gauge factor of BCC and FCC cellular composites(4 wt% of MWCNT) with a relative density of 30%was observed to be 46.4 and 30.2 respectively, under compression. The higher sensitivity of the BCC plate-lattice could be attributed to its higher degree of stretching-dominated deformation behavior than the FCC plate-lattice, which exhibits bending-dominated behavior. The 3D printed cellular PPR/MWCNT composites structures were found to show excellent piezoresistive self-sensing characteristics and open new avenues for in situ structural health monitoring in various applications.

Review of surfactant-assisted chemical enhanced oil recovery for carbonate reservoirs: challenges and future perspectives

A significant fraction of the conventional oil reserves globally is in carbonate formations which contain a substantial amount of residual oil. Since primary and secondary recovery methods fail to yield above 20%-40%of original oil in place from these reserves, the need for enhanced oil recovery（EOR） techniques for incremental oil recovery has become imperative. With the challenges presented by the highly heterogeneous carbonate rocks,evaluation of tertiary-stage recovery techniques including chemical EOR（c EOR） has been a high priority for researchers and oil producers. In this review, the latest developments in the surfactant-based c EOR techniques applied in carbonate formations are discussed, contemplating the future direction of existing methodologies. In connection with this, the characteristics of heterogeneous carbonate reservoirs are outlined. Detailed discussion on surfactant-led oil recovery mechanisms and related processes, such as wettability alteration, interfacial tension reduction, microemulsion phase behavior, surfactant adsorption and mitigation, and foams and their applications is presented. Laboratory experiments, as well as field study data obtained using several surfactants, are also included.This extensive discussion on the subject aims to help researchers and professionals in the field to understand the current situation and plan future enterprises accordingly.

A review of CO2 storage in geological formations emphasizing modeling,monitoring and capacity estimation approaches

The merits of CO2 capture and storage to the environmental stability of our world should not be underestimated as emissions of greenhouse gases cause serious problems.It represents the only technology that might rid our atmosphere of the main anthropogenic gas while allowing for the continuous use of the fossil fuels which still power today’s world.Underground storage of CO2 involves the injection of CO2 into suitable geological formations and the monitoring of the injected plume over time,to ensure containment.Over the last two or three decades,attention has been paid to technology developments of carbon capture and sequestration.Therefore,it is high time to look at the research done so far.In this regard,a high-level review article is required to provide an overview of the status of carbon capture and sequestration research.This article presents a review of CO2 storage technologies which includes a background of essential concepts in storage,the physical processes involved,modeling procedures and simulators used,capacity estimation,measuring monitoring and verification techniques,risks and challenges involved and field-/pilot-scale projects.It is expected that the present review paper will help the researchers to gain a quick knowledge of CO2 sequestration for future research in this field.

Thermal and microstructural characterization of a novel ductile cast iron modified by aluminum addition

In high-temperature applications,like exhaust manifolds,cast irons with a ferritic matrix are mostly used.However,the increasing demand for higher-temperature applications has led manufacturers to use additional expensive materials such as stainless steels and Ni-resist austenitic ductile cast irons.Thus,in order to meet the demand while using low-cost materials,new alloys with improved high-temperature strength and oxidation resistance must be developed.In this study,thermodynamic calculations with Thermo-Calc software were applied to study a novel ductile cast iron with a composition of 3.5wt%C,4wt%Si,1wt%Nb,0‒4wt%Al.The designed compositions were cast,and thermal analysis and microstructural characterization were performed to validate the calculations.The lowest critical temperature of austenite to pearlite eutectoid transformation,i.e.,A1,was calculated,and the solidification sequence was determined.Both calculations and experimental data revealed the importance of aluminum addition,as the A1 increased by increasing the aluminum content in the alloys,indicating the possibility of utilizing the alloys at higher temperature.The experimental data validated the transformation temperature during solidification and at the solid state and confirmed the equilibrium phases at room temperature as ferrite,graphite,and MC-type carbides.

Synthesis and Characterization of Porous Carbon from Petroleum Pitch Using KOH

Preparation and process optimization of porous carbons using different carbon sources and activating agents are frequently and commonly reported in open literature. However, only scanty references are made on utilization of petroleum coke for conversion to high surface area porous carbon using KOH as the activating agent. Hence, the present work attempts a process optimization exercise to prepare high surface area porous carbon from Petroleum coke using chemical activation (KOH) utilizing design of experiments. The effect of activation temperature, petroleum coke to KOH ratio (KPR) and activation duration were assessed on the surface area and yield of the porous carbon. The process optimization was performed covering experimental parameters in the range of 500?C - 800?C, 2 - 5 and 30 - 120 min. The optimal process conditions for maximizing the yield and BET surface area was identified to be an activation temperature of 639?C, KPR of 4.5 and activation duration of 43 min, having BET surface area 1765 m2/g and yield of 89.8%. However, an attempt to maximize only the BET surface area, ignoring yield has resulted with a porous carbon with maximum surface area of 2061 m2/g, with the optimal process conditions being an activation temperature of 688?C, KPR of 3.8 and activation duration of 74 min, with the corresponding yield of only 77%. The characterization of porous carbon was performed using nitrogen adsorption isotherm, FT-IR and SEM analysis.

Additive manufacturing of sustainable biomaterials for biomedical applications

Biopolymers are promising environmentally benign materials applicable in multifarious applications.They are especially favorable in implantable biomedical devices thanks to their excellent unique properties,including bioactivity,renewability,bioresorbability,biocompatibility,biodegradability and hydrophilicity.Additive manufacturing(AM)is a flexible and intricate manufacturing technology,which is widely used to fabricate biopolymer-based customized products and structures for advanced healthcare systems.Three-dimensional(3D)printing of these sustainable materials is applied in functional clinical settings including wound dressing,drug delivery systems,medical implants and tissue engineering.The present review highlights recent advancements in different types of biopolymers,such as proteins and polysaccharides,which are employed to develop different biomedical products by using extrusion,vat polymerization,laser and inkjet 3D printing techniques in addition to normal bioprinting and four-dimensional(4D)bioprinting techniques.It also incorporates the influence of nanoparticles on the biological and mechanical performances of 3D-printed tissue scaffolds,and addresses current challenges as well as future developments of environmentally friendly polymeric materials manufactured through the AMtechniques.Ideally,there is a need for more focused research on the adequate blending of these biodegradable biopolymers for achieving useful results in targeted biomedical areas.We envision that biopolymer-based 3D-printed composites have the potential to revolutionize the biomedical sector in the near future.

Numerical and safety considerations about the Daguangbao landslide induced by the 2008 Wenchuan earthquake

The 2008 Wenchuan earthquake resulted in a large number of fatalities and caused significant economic losses.Thousands of landslides,many of which are very large,were triggered by the earthquake.A majority of catastrophic landslides were distributed along the central Longmenshan fault system,at the eastern margin of the Tibetan Plateau.Some of the landslides resulted in sudden damming of rivers causing flooding,which in turn induced secondary sliding disasters.Among the most significant landslides,the Daguangbao landslide was the largest in volume with the maximum thickness.For this,a numerical model of the Daguangbao landslide,using the material point method(MPM),was developed to simulate the interaction of the seismic loads imposed on the slope.The numerical results then are compared with the post-earthquake profile.As a consequence of the landslide,a nearly vertical head scarp with a maximum height of about 700 m was generated.This is considered as a high risk situation that requires constant monitoring and evaluation.Finally,we propose a methodology based on Bayesian networks(BNs)to manage the risk associated with the stability of the rockwall at the Daguangbao landslide site.

Review of current progress in hole-transporting materials for perovskite solar cells

Recent advancements in perovskites’ application as a solar energy harvester have been astonishing. The power conversion efficiency(PCE) of perovskite solar cells(PSCs) is currently reaching parity(>25 percent), an accomplishment attained over past decades. PSCs are seen as perovskites sandwiched between an electron transporting material(ETM) and a hole transporting material(HTM). As a primary component of PSCs, HTM has been shown to have a considerable effect on solar energy harvesting, carrier extraction and transport, crystallization of perovskite, stability, and price. In PSCs, it is still necessary to use a HTM.While perovskites are capable of conducting holes, they are present in trace amounts, necessitating the use of an HTM layer for efficient charge extraction. In this review, we provide an understanding of the significant forms of HTM accessible(inorganic, polymeric and small molecule-based HTMs), to motivate further research and development of such materials. The identification of additional criteria suggests a significant challenge to high stability and affordability in PSC.

Corrosion inhibition of layered double hydroxides for metal-based systems

Layered double hydroxide(LDH),a kind of 2D layered materials,has been recognized as the promising anticorrosion materials for metal and its alloy.The microstructure,physical/chemical properties,usage in corrosion inhibition and inhibition performance of LDH have been studied separately in open literature.However,there is a lack of a complete review to summarize the status of LDH technology and the potential R&D opportunities in the field of corrosion inhibition.In addition,the challenges for LDH in corrosion inhibition of metal-based system have not been summarized systematically.Herein,we review recent advances in the rational design of LDH for corrosion inhibition of metal-based system(i.e.Mg alloy,Al alloy,steel and concrete)and high-throughput anticorrosion materials development.By evaluating the physical/chemical properties,usage in metal-based system and the corrosion inhibition mechanism of LDH,we highlight several important factors of LDH for anticorrosion performance and common features of LDH in applying different metal alloys.Finally,we provide our perspective and recommendation in this field,including high-throughput techiniques for combinatorial compositional design and rapid synthesis of anticorrosion alloys,with the goal of accelerating the development and application of LDH in corrosion inhibition of metal-based system.

Optimizing the oxide support composition in Pr-doped CeO_(2) towards highly active and selective Ni-based CO_(2) methanation catalysts

In this study,Ni catalysts supported on Pr-doped Ce O_(2) are studied for the CO_(2) methanation reaction and the effect of Pr doping on the physicochemical properties and the catalytic performance is thoroughly evaluated.It is shown,that Pr^(3+)ions can substitute Ce^(4+)ones in the support lattice,thereby introducing a high population of oxygen vacancies,which act as active sites for CO_(2) chemisorption.Pr doping can also act to reduce the crystallite size of metallic Ni,thus promoting the active metal dispersion.Catalytic performance evaluation evidences the promoting effect of low Pr loadings(5 at%and 10 at%)towards a higher catalytic activity and lower CO_(2) activation energy.On the other hand,higher Pr contents negate the positive effects on the catalytic activity by decreasing the oxygen vacancy population,thereby creating a volcano-type trend towards an optimum amount of aliovalent substitution.

Effects of trapping number on biopolymer flooding recovery of carbonate reservoirs

The effects of trapping number on enhanced oil recovery by schizophyllan biopolymer flooding in carbonate reservoirs were investigated by running several 1D simulations using measured reservoir rock and fluid data.Sensitivity analysis was performed on different uncertain parameters to history match the oil recovery obtained in the core flooding experiment.These parameters include inaccessible pore volume(IPV),biopolymer adsorption,permeability reduction factor,shear rate coefficient,hardness of injection water,and trapping number.The IPV,biopolymer adsorption,permeability reduction factor,shear rate coefficient and hardness of injection water have negligible effects on oil recovery by biopolymer flooding.Also,history matching of oil recovery data was not possible when these parameters were varied within their typical range of values.When trapping number effect was considered through capillary desaturation curve(CDC),residual oil saturation was reduced from 25.1%without considering its effect or under low trapping number to 10.0%,and the fitting effect for recovery was better.Therefore,we can’t neglect the trapping number effect during biopolymer flooding simulation in the carbonate reservoirs.

Nonlinear elastic constitutive relations of residually stressed composites with stiff curved fibres

Mechanical models of residually stressed fibre-reinforced solids,which do not resist bending,have been developed in the literature.However,in some residually stressed fibre-reinforced elastic solids,resistance to fibre bending is significant,and the mechanical behavior of such solids should be investigated.Hence,in this paper,we model the mechanical aspect of residually stressed elastic solids with bending stiffness due to fibre curvature,which up to the authors’knowledge has not been mechanically modeled in the past.The proposed constitutive equation involves a nonsymmetric stress and a couple-stress tensor.Spectral invariants are used in the constitutive equation,where each spectral invariant has an intelligible physical meaning,and hence they are useful in experiment and analysis.A prototype strain energy function is proposed.Moreover,we use this prototype to give results for some cylindrical boundary value problems.

Decoupled δ^(13)Ccarb and δ^(13)Corg records at Triassic–Jurassic boundary interval in eastern Tethys: Environmental implications for spatially different global response

Althoughδ^(13)C data(eitherδ^(13)Ccarb orδ^(13)Corg)ofmany Triassic–Jurassic(T-J)sections have been acquired,pairedδ^(13)Ccarb andδ^(13)Corg from continuous T-J carbonate sections,especially in eastern Tethys,have been scarcely reported.This study presents paired and decoupledδ^(13)Ccarb andδ^(13)Corg data from a continuous T-J carbonate section in Wadi Naqab.The T-J Wadi Naqab carbonate section,located in United Arab Emirates,Middle East,represents tropical and shallow marine sedimentation in eastern Tethys.At the T-J boundary interval,an initial carbon isotope excursion(CIE)is observed with different magnitude of isotope excursion and timing inδ^(13)Ccarb andδ^(13)Corg,while subsequently a positive CIE is only distinct inδ^(13)Ccarb.Based on petrological,carbon isotope,Rock-Eval and elemental analyses,theδ^(13)Ccarb is thought to record marine inorganic carbon,and theδ^(13)Corg to record terrigenous organic carbon.Therefore,the pairedδ^(13)Ccarb andδ^(13)Corg herein potentially document simultaneous changes in T-J atmospheric and marine settings of eastern Tethys.Their decoupled behavior may likely be caused by different changes or evolution of carbon pool between marine and atmospheric settings.The initial CIE present in bothδ^(13)Ccarb andδ^(13)Corg may indicate influence of isotopically light carbon release related to CAMP activity in both atmospheric and marine settings.The following positive CIE only inδ^(13)Ccarb suggests relatively steady carbon isotope composition in atmosphere,but enhanced burial of isotopically light carbon in marine settings.Furthermore,the T-J carbonates in the studied section were possibly deposited in normal and oxic shallow marine conditions.Global correlation based on the Wadi Naqab section and other T-J sections suggests spatially different T-J environmental parameters:in eastern Tethys and western Panthalassa,oxic condition,lacking organic-rich sediment,weaker ocean acidification and less influence of isotopically light carbon are more prevalent;in western Tethys and eastern Panthalassa,oxygen-depleted condition,black shales,stronger acidification and heavier influence of isotopically light carbon are more prevalent.These differences may be related to spatial distance from the CAMP or to different paleogeography.

Free vibration characteristics of sectioned unidirectional/bidirectional functionally graded material cantilever beams based on finite element analysis

Advancements in manufacturing technology,including the rapid development of additive manufacturing(AM),allow the fabrication of complex functionally graded material(FGM)sectioned beams.Portions of these beams may be made from different materials with possibly different gradients of material properties.The present work proposes models to investigate the free vibration of FGM sectioned beams based on onedimensional(1D)finite element analysis.For this purpose,a sample beam is divided into discrete elements,and the total energy stored in each element during vibration is computed by considering either the Timoshenko or Euler-Bernoulli beam theory.Then,Hamilton’s principle is used to derive the equations of motion for the beam.The effects of material properties and dimensions of FGM sections on the beam’s natural frequencies and their corresponding mode shapes are then investigated based on a dynamic Timoshenko model(TM).The presented model is validated by comparison with three-dimensional(3D)finite element simulations of the first three mode shapes of the beam.

Numerical Simulation of Turbulent Swirling Pipe Flow with an Internal Conical Bluff Body

Turbulent swirling flow inside a short pipe interacting with a conical bluff body was simulated using the commercial CFD code Fluent.The geometry used is a simplified version of a novel liquid/gas separator used in multiphase flow metering.Three turbulence models,belonging to the Reynolds averaged Navier-Stokes(RANS)equations framework,are used.These are,RNG k-ε,SST k-ωand the full Reynolds stress model(RSM)in their steady and unsteady versions.Steady and unsteady RSM simulations show similar behavior.Compared to other turbulence models,they yield the best predictions of the mean velocity profiles though they exhibit some discrepancies in the core region.The influence of the Reynolds number on velocity profiles,swirl decay,and wall pressure on the bluff body are also presented.For Reynolds numbers generating a Rankine-like velocity profile,the width and magnitude of flow reversal zone decreases along the pipe axis disappearing downstream for lower Reynolds numbers.The tangential velocity peaks increase with increasing Reynolds number.The swirl decay rate follows an exponential form in accordance with the existing literature.These flow features would affect the performance of the real separator and,thus,the multiphase flow meter,noticeably.

On the Number of Idempotent Partial Contraction Mappings of a Finite Chain

Let be the partial symmetric semigroup on and let and be its subsemigroups of order-preserving contractions and order-preserving, order-decreasing contractions mappings of , respectively. In this paper we investigate the cardinalities of and , the set idempotents of and , respectively. We also investigate the cardinalities of certain equivalences on and .

黏弹性VTI介质中敏感度核函数:地震波复走时关于弹性模量及Q值偏导数的计算

实际地层中地震波传播普遍存在速度和衰减各向异性现象,研究黏弹各向异性介质中高频地震波传播理论有助于揭示地震波的传播特征.本文针对黏弹性VTI介质,从Christoffel矩阵的解析特征值出发推导出qP、qSV和qSH波的复相速度和复射线速度的解析表达式,并应用实射线追踪方法确定出均匀复射线速度矢量,由此计算出实射线速度和实射线衰减以及实射线品质因子.基于非均匀复相速度和均匀复射线速度的解析表达式,推导了实射线慢度和实射线衰减关于黏弹性模量(包括弹性模量和Q值)的敏感度核函数,该敏感度核函数反映各个黏弹性模量对地震波复走时的影响程度.不同岩石样本的数值计算结果显示,实走时对弹性模量更为敏感,而射线衰减(虚走时)对弹性模量和Q值的敏感程度相当.本研究可为黏弹性VTI介质中地震射线追踪和复走时层析成像提供理论基础.

SmokerViT: A Transformer-Based Method for Smoker Recognition

Smoking has an economic and environmental impact on society due to the toxic substances it emits.Convolutional Neural Networks(CNNs)need help describing low-level features and can miss important information.Moreover,accurate smoker detection is vital with minimum false alarms.To answer the issue,the researchers of this paper have turned to a self-attention mechanism inspired by the ViT,which has displayed state-of-the-art performance in the classification task.To effectively enforce the smoking prohibition in non-smoking locations,this work presents a Vision Transformer-inspired model called SmokerViT for detecting smokers.Moreover,this research utilizes a locally curated dataset of 1120 images evenly distributed among the two classes(Smoking and NotSmoking).Further,this research performs augmentations on the smoker detection dataset to have many images with various representations to overcome the dataset size limitation.Unlike convolutional operations used in most existing works,the proposed SmokerViT model employs a self-attention mechanism in the Transformer block,making it suitable for the smoker classification problem.Besides,this work integrates the multi-layer perceptron head block in the SmokerViT model,which contains dense layers with rectified linear activation and linear kernel regularizer with L2 for the recognition task.This work presents an exhaustive analysis to prove the efficiency of the proposed SmokerViT model.The performance of the proposed SmokerViT performance is evaluated and compared with the existing methods,where it achieves an overall classification accuracy of 97.77%,with 98.21%recall and 97.35%precision,outperforming the state-of-the-art deep learning models,including convolutional neural networks(CNNs)and other vision transformer-based models.

A review of control strategies used for morphing aircraft applications

This paper reviews the various control algorithms and strategies used for fixed-wing morphing aircraft applications. It is evident from the literature that the development of control algorithms for morphing aircraft technologies focused on three main areas. The first area is related to precise control of the shape of morphing concepts for various flight conditions. The second area is mainly related to the flight dynamics, stability, and control aspects of morphing aircraft. The third area deals mainly with aeroelastic control using morphing concepts either for load alleviation purposes and/or to control the instability boundaries. The design of controllers for morphing aircraft/wings is very challenging due to the large changes that can occur in the structural, aerodynamic, and inertial characteristics. In addition, the type of actuation system and actuation rate/speed can have a significant effect on the design of such controllers. The aerospace community is in strong need of such a critical review especially as morphing aircraft technologies move from fundamental research at a low Technology Readiness Level(TRL) to real-life applications. This critical review aims to identify research gaps and propose future directions. In this paper, research activities/papers are categorized according to the control strategy used. This ranges from simple Proportional Integral Derivative(PID) controllers at one end to complex robust adaptive controllers and deep learning algorithms at the other end. This includes analytical, computational, and experimental studies. In addition, the various dynamic models used and their fidelities are highlighted and discussed.